Welcome to the I Can't Sleep Podcast,
Where I help you drift off one fact at a time.
I'm your host Benjamin Boster and today's episode is about the platypus.
The platypus,
Sometimes referred to as the duck-billed platypus,
Is a semi-aquatic egg-laying mammal endemic to eastern Australia,
Including Tasmania.
The platypus is the sole living representative of its family,
Ornithorhynchidae,
And genus Ornithorhynchus,
Though a number of related species appear in the fossil record.
Together with the four species of echidna,
It is one of the five extant species of monotremes,
Mammals that lay eggs instead of giving birth to live young.
Like other monotremes,
The platypus has a sense of electrolocation,
Which it uses to detect prey in water while its eyes,
Ears,
And nostrils are closed.
It is one of the few species of venomous mammals,
As the male platypus has a spur on each hind foot that delivers an extremely painful venom.
The unusual appearance of this egg-laying,
Duck-billed,
Beaver-tailed mammal at first baffled European naturalists.
In 1799,
The first scientists to examine the preserved platypus body judged it a fake made of several animals sewn together.
The unique features of the platypus make it important in the study of evolutionary biology.
And a recognizable and iconic symbol of Australia.
It is culturally significant to several aboriginal peoples who also used to hunt it for food and has appeared on stamps and currency.
Australian Aboriginal people have referred to the platypus in various ways,
Depending on Australian indigenous languages and dialects.
Among the names found,
Bundaburra.
Malangong.
TEMBREET WATJARANG Names in Yas,
Murumbaji,
And Thumud THONBAK Region of Gumbura Darlingdowns TULIWARUNG or TULIWARUNG Waywaran language.
Wawundjeri,
Victoria.
JANBANG BANJULUNG,
QLD JUMULUNG YUAN LANGUAGE YUAN,
NSW Malungan.
Gunawa language,
Gunawa Australia Capital Territory.
Tlidurang,
Chamul,
Chamalung,
Urni,
Tangadani,
Wiradjuri language,
Wiradjuri Victoria New South Wales,
Una,
Etc.
The name chosen and approved in Palawan Kani,
Reconstructed Tasmanian Language,
Is Larila.
When the platypus was first encountered by Europeans in 1798,
Hippeld and Sketch were sent back to Great Britain by Captain John Hunter,
The second Governor of New South Wales.
British scientists' initial hunch was that the attributes were a hoax.
George Shaw,
Who produced the first description of the animal in The Naturalist's Miscellany in 1799,
Stated it was impossible not to entertain doubts as to its genuine nature.
And Robert Knox believed,
Because it arrived in England via the Indian Ocean,
That it might have been created by Chinese sailors.
It was thought somebody had sewn a duck's beak onto the body of a beaver-like animal.
Shaw used a pair of scissors to check for stitches.
The common name platypus means flat foot,
Deriving from the Greek word platypus,
From platus,
Broad,
Wide,
Flat,
And pus,
Foot.
Shah initially assigned the species the Linnaean name Platypus anittinus when he described it,
But the genus term was quickly discovered to already be in use as the name of a beetle genus,
Platypus.
It was independently described as Ornithorhynchus paradoxus by Johann Blumenbach in 1800,
From a specimen given to him by Sir Joseph Banks.
And following the rules of priority of nomenclature,
It was later officially recognized as Ornithorhynchus anatinus.
Various dictionaries list platypuses or simply platypus as the plural.
Alternatively,
The term platypi is also used for the plural,
Although this is a form of pseudo-Latin.
Going by the word's Greek roots,
The plural would be platypides.
Early European settlers called it by many names,
Such as water mole,
Duck bill,
And duck mole.
Occasionally it is specifically called the duck-billed platypus.
There is no official term for platypus young,
But the term platypub sees unofficial use,
As does bugle.
The scientific name Ornithorhynchus annatinus literally means duck-like bird snout.
Deriving the genus name from the Greek root ornith,
Bird,
And the word runcus,
Beak.
Its species name is derived from Latin anadinus,
Duck-like,
From anus,
Duck.
The platypus is the sole living representative or mototypic taxon of its family.
Most of the platypus's small streamlined body is covered with short dense brown fur that traps a layer of insulating air to keep the animal warm both in and out of water.
The fur coat is waterproof and consists of flattened guard hairs and curvy under fur hairs.
It is one of the most densely furred mammals,
Behind only otters.
It is also biofluorescent and glows cyan and green when under ultraviolet light.
This may serve to camouflage it in low lighting from UV sensitive predators.
It is also unique among mammal in having hair pigmentation melanosomes that are hollow.
The duck-like bill consists of a long snout and lower jaw,
Which is covered in soft skin.
The nostrils are located near the tip of the snout's dorsal surface,
While the eyes and ears are just behind the snout in a groove which closes underwater.
It has cheek pouches for storing food.
The platypus's wide,
Flat tail is compared to a beaver's,
But is furry rather than scaly.
It stores fat reserves and can act as a rudder during swimming.
The legs are short and have a sprawling stance.
Webbing is more significant on the front feet.
While walking on land,
The feet are folded up and knuckle walking to protect the webbing.
The platypus has an interclavicle in the shoulder girdle,
A trait which they share in common with reptiles.
As in many other aquatic and semi-aquatic vertebrates,
The bones show osteosclerosis,
Increasing their density to reduce buoyancy.
Adult platypuses lack teeth and instead have heavily keratinized food grinding pads.
Young platypuses have one premolar tooth,
And two molars on each maxillae,
And three molars on the dendries.
The first upper and third lower cheek teeth have only one major cusp,
While the rest have two.
They lose their teeth around the time they leave their natural burrow.
The platypus lacks a functional stomach due to the lack of genes necessary for creating and secreting pepsin proteases.
However,
The platypus' digestive tract has a pouch-like section that assists with nutrient absorption in the intestines.
Male platypuses have an average length of 50 cm and weight of 1700 g,
While females are smaller with an average length of 43 cm and weight of 900 g.
The species follows Bergman's rule,
With individuals being larger the farther south they are due to colder climates.
There are local variations,
However.
The platypus has an average body temperature of about 32 degrees Celsius,
Lower than the 37 degrees Celsius typical of placental mammals.
Research suggests this has been a gradual adaptation to harsh environmental conditions among the few marginal surviving monotreme species,
Rather than a general characteristic of past monotremes.
Monotremes are the only mammals apart from the Guiana dolphin known to have a sense of electroreception.
The platypus relies on electrolocation when feeding,
As the eyes,
Ears,
And nose are closed while underwater.
Digging in the bottom of streams with its bill,
Its electroreceptors detect tiny electric currents generated by the muscular contractions of its prey.
Experiments have shown that platypus will even react to an artificial shrimp if a small electric current is passed through it.
The 40,
000 electroreceptors are arranged in rows in the skin of the bill from front to back,
While mechanoreceptors for touch are uniformly distributed across the bill.
The electrosensory area of the cerebral cortex is in the tactile somatosensory area,
And some cortical cells receive input from both electroreceptors and mechanoreceptors,
Suggesting the platypus feels electric fields as touches.
These receptors in the build dominate the somatotopic map of the platypus brain.
In the same way,
Human hands dominate the Penfield homunculus map.
The platypus can feel the direction of an electric source,
Perhaps by comparing differences in signal strength across the array of electroreceptors,
Enhanced by the characteristic side-to-side motion of the animal's head while hunting.
It may also be able to determine the distance of moving prey via the timing difference between electrical and mechanical pressure sensations.
Monitoring electrolocation for hunting in murky waters may be tied to their tooth loss.
The extinct obduradon was electroreceptive,
But unlike the modern platypus,
It foraged in open water.
The eyes of the platypus have basal traits also found in lungfish and amphibians,
Such as floral cartilage,
Double cones,
And droplets.
The platypus's eyes are small and shut underwater.
Though several features indicate its ancestors relied on vision.
As with other aquatic mammals,
The eye has a flattened cornea and surrounding lens,
While the posterior surface of the lens is sharply inclined.
A temporal ear-side concentration of retinal ganglion cells,
Important for binocular vision,
Indicates a vestigial role in predation,
Though the actual visual acuity is insufficient for such activities.
Limited acuity is matched by low cortical magnification,
A small lateral geniculate nucleus,
And a large optic tectum,
Suggesting that the visual midbrain plays a more important role than the visual cortex,
As in some rodents.
These features suggest that the platypus has adapted to an aquatic and nocturnal lifestyle,
Developing its electro-sensory system at the cost of its visual system.
This contrasts with the small number of electroreceptors in the short-beaked echidna,
Which dwells in dry environments,
While the long-beaked echidna,
Which lives in wetter habitats,
Is intermediate between the other two monotremes.
The ears of the platypus are adapted for hearing while out of water.
As in all true mammals,
It has three middle ear bones,
Though the cochlea lacks spirals,
But is described as well organized.
Within the cochlea there are rows of inner and outer hair cells.
As in placental mammals,
The outer hair cells of the platypus are adapted for hearing high frequencies,
Suggesting it is an ancestral mammalian trait.
However,
It also possesses more rows of inner hair cells.
The olfactory smelling systems of the platypus and the echidna independently evolved from an ancestor with less advanced smelling.
The main olfactory bulb of the platypus lacks the complex layers of the echidna,
While both the piriform cortex and flabs are simpler.
Monotremes differ from placental mammals in that their mitral cells are distributed throughout the outer plexiform layer of the olfactory bulb,
Rather than packed as a monolayer.
While both male and female platypuses are born with back ankle spurs,
Only the males retain them into adulthood.
Similar spurs are found on many archaic mammal groups,
Indicating that this was an ancient general characteristic among mammals.
The spurs of the male inject venom,
Which is powerful enough to inflict pain in humans.
Starting from the wounded area,
The affected limb develops edema,
Swelling via fluid buildup,
Which can lead to an excruciating hypererglesia,
Heightened sensitivity to pain,
That can last as long as months.
The venom is composed largely of defensin-like proteins,
DLPs,
Produced by the immune system,
Some of which are unique to the species.
It is produced in kidney-shaped alveolar glands located in each of the thighs of the hind limbs and connected to the spur.
The venomous spurs of male platypuses serve as weapons in battle with other males for breeding.
The platypus is native to the freshwaters of eastern Australia,
From Queensland to Tasmania.
It was believed to be extinct on the South Australian mainland.
It was the last sighting recorded at Renmark in 1975.
Platypuses were captively bred at Warn Wong Sanctuary in 1990-91.
In October 2020,
A nesting platypus was filmed in the wild after the previously abandoned sanctuary reopened.
There is a population on Kangaroo Island introduced in the 1920s said to stand at 150 individuals in the Rocky River region of Flinders Chase National Park.
The platypus is semi-aquatic and requires permanent freshwater habitat.
Its swimming style is unique among mammals,
Propelling itself by alternating strokes in each front foot,
While the webbed hind feet and tail are used for steering.
It can maintain its relatively low body temperature when feeding in colder depths of below 5 degrees Celsius.
In one study,
Dives lasted on average 35 seconds,
With surfacing intervals averaging 13 seconds.
The species is mainly nocturnal,
But is also active at dusk during the summer and daytime during the winter.
A platypus may spend half the day in water and then retreat into its burrow,
Which is constructed by digging into the bank.
These vary between simple resting banks and complex nesting breeding burrows.
It may have a range of up to 7 km,
With a male's home range overlapping those of 3 or 4 females.
Oedipuses are not very vocal.
They have been recorded to growl when disturbed and squeak when feeling pain.
The platypus is a carnivore and forages by probing along the bottom.
It feeds on insect larvae,
Antelope worms,
Shrimp,
Crayfish,
Bivalves,
Tadpoles,
And fish eggs.
It stores food in its cheek pouches for later consumption.
In captivity,
Platypuses have survived up to 30 years,
And wild specimens have been recaptured at 24 years old.
They are preyed upon by Murray Cod,
Eels,
Carpet Snakes,
Guanas,
Eagles,
Crocodiles,
And Foxes.
Parasites and viruses also affect their mortality,
Though platypuses appear to have a high tolerance for them.
Externally,
Platypuses may carry fleas,
Mites,
And ticks,
The latter being more prominent in young.
Platypuses are seasonal breeders,
With some more southerly populations breeding later in the year than those further north,
Those in New South Wales made during fall and winter.
During incubation and weaning,
The mother initially leaves the burrow only for short periods to forage.
She leaves behind her a number of thin soil plugs along the length of the burrow.
Pushing past these on her return squeezes water from her fur and allows the burrow to remain dry.
The female spends less time with her offspring after five weeks,
Who emerge from the burrow around four months.
By then they are fully covered in fur and may be around 67% the weight of an adult and 80% the length.
Juvenile males disperse further than females.
They are fully grown at around 2 years.
In separate publications in 1934,
1947,
And 1951,
William King Gregory theorized that placental mammals and marsupials may have diverged earlier,
And a subsequent branching divided the monotremes and marsupials.
Later research and fossil discoveries have suggested this is incorrect.
Modern monotremes are the survivors of an early branching of the mammal tree,
And a later branching is thought to have led to the marsupial and placental groups.
Both molecular clock and fossil dating suggest that the platypus split from echidnas around 19 to 48 million years ago.
The oldest discovered fossil of the modern platypus dates back to about 100,
000 years ago,
During the Quaternary period.
Though a limb bone of Ornithorhynchus is known from Pliocene epic Strata.
The extinct monotremes from the Cretaceous period are considered to be basal to the platypus and echidnas.
The remains of one were discovered in New South Wales,
Composed of an opalized lower jawbone with three molar teeth.
The Malartese were initially thought to be Tribosphenic,
Which would have supported a variation of Gregory's theory.
But later research has suggested that while they have three cusps,
They evolved under a separate process.
The fossil jaw of another is elongated,
But unlike modern platypuses and echidnas,
Lacks a beak.
The platypus has been a subject in the Dreamtime stories of Aboriginal Australians,
Some of whom believe the animal was a hybrid of a duck and a water rat.
Aboriginals from the Upper Darling River region have a story of a large water rat called Bagoon who kidnaps a duck what wandered too far from its tribe.
After managing to escape,
She returned and laid two eggs,
Which hatched the first platypuses.
They were all exiled and went to live in the mountains.
In another story from the Upper Darling,
The major animal groups,
The land animals,
Water animals,
And birds,
All competed for the platypus to join their respective groups.
But the platypus ultimately decided to not join any of them,
Feeling that he did not need to be part of a group to be special,
And wished to remain friends with all of those groups.
The platypus is also featured as a totem for some aboriginal peoples,
Which is to them a natural object,
Plant or animal that is inherited by members of a clan or family as their spiritual emblem.
And the animal holds special meaning for the Wondiwondi people at the Murray River.
Because of their cultural significance and importance in connection to country,
The platypus is protected and conserved by these indigenous peoples.
The platypus has often represented Australia's cultural identity,
And its image has also been used for stamps and currency,
And as a mascot in the 2000 Summer Olympics in Sydney.
